1. Technical Field
The inventive arrangements relate generally to methods and apparatus providing advanced operating features for audio only, video only and both video and audio programs recorded on disc media, for example recordable digital video discs, hard drives and magneto optical discs.
2. Description of the Related Art
Various devices have been developed to enable consumers to record video and/or audio programs for later presentation. Such devices include tape recorders, video cassette recorders, recordable compact discs, and most recently, recordable digital video discs (DVD). Hard drives and magneto optical discs have also been used.
A DVD that can be recorded on only once, and thereafter is essentially a DVD read only memory, is referred to by the acronym DVD-R. The acronym DVD-R is also used generally to refer to the write-once, or record-once, technology. Several formats are available for DVD's to be recorded on, erased and re-recorded; that is, overwritten or rewritten. These are referred to by the acronyms DVD-RAM, DVD-RW and DVD+RW. As of this time no uniform industry standard has been adopted. The acronyms DVD-RAM, DVD-RW and DVD+RW are also used generally to refer to the respective rewritable technologies. Reference herein to rewritable DVD technology, devices and methods is generally intended to encompass all of the standards which are now being used, as well as those which may be developed in the future.
In many cases, the program presentations are recorded in the viewer and/or listener's absence, for presentation at a later, more convenient time. This is referred to as time shifting the program. At other times, a program is being viewed and/or listened to without being recorded, and with out any interest in a recording, but the viewer's and/or listener's attention is interrupted, for example by a telephone call or an unexpected visitor. If the viewer and/or listener is watching a television program, for example, and has a cassette tape in a VCR, or can retrieve and load such a cassette tape quickly, the program can be recorded. However, the viewer and/or listener cannot view and/or listen to the program in its entirety, and in a proper time sequence, until after the recording has been completed. The time to completion of the recording can be short or long, depending on the length of the program.
Although rewritable DVD technology is generally available, operation is limited to such basic functions as play, record, fast forward reverse and stop. Pause is available, but only as a counterpart to pause operation in a VCR, for example interrupting the play back of a prerecorded program or interrupting the recording of a viewed program to eliminate commercials from the recording. Unlike computer hard drives, recordable DVD devices have a very significant additional function, which is playing back prerecorded DVD's. Thus, there is an economic incentive to develop rewritable DVD technology, including methods and devices, that can be used instead of a computer hard drive. It is a challenge to provide such devices with improved, advantageous features without compromising the goal of decreasing costs and increasing sales.
A group of pictures (GOP) stored on DVD media is typically contained within a logical unit referred to as a video object unit (VOBU). Typically, the VOBU contains about 12 or 16 pictures, together with associated audio data. Further, each VOBU begins with exactly one navigation pack (NV_PCK). The NV_PCK conventionally contains presentation control information (PCI) as well as disc search information (DSI) for the video object unit in which they are included. The presentation control information contains details of the timing and presentation of a program. The disc search information is composed of relative addresses of NV packs of VOBUs in the forward and backward directions. Each NV_PCK also includes the data size of the first reference picture in a GOP and the end address for the first three reference pictures in the VOBU. This is the only clue given as to the structure of the VOBU.
The disc search information is useful in performing “trick” modes of playback, that is, any mode of disc player operation other than normal play, stop and pause. One aspect of conventional disc search information (DSI) is that it helps the decoder to find I pictures within the VOBU corresponding to the current NV_PCK. The NV_PCK also contains data which helps the decoder to find VOBUs far into the future or past of presentation, relative to the current VOBU. The VOBUs in the past relative to the current VOBU presentation are referenced in fields of the NV_PCK known as the BWDI (backward information). The VOBUs in the future relative to the current VOBU presentation are referenced in fields of the NV_PCK known as FWDI (forward information). The conventional DSI data does permit, to a limited extent, special display modes involving reproduction of video. For example, in conventional systems, fast forwarding and rewinding are made possible by reproducing only the reference I pictures of VOBUs having a predetermined time interval between them. The predetermined time interval chosen is generally a function of the relative rate of forwarding and rewinding. However, because of the limited amount of information contained within conventional NV_PCKs the flexibility of display in trick modes is severely limited. For example, the NV_PCK data does not include much information regarding the internal structure of each GOP contained within a VOBU.